Method for demulsifying emulsions

ABSTRACT

A process for breaking an emulsion into a water phase and an oil phase involving: (a) providing an emulsion containing an oil phase and a water phase; (b) providing an alkoxylated C 10-24  carboxylic acid ester derived by the addition of ethylene oxide and/or propylene oxide onto a ring opened epoxidized C 10-24  carboxylic acid triglyceride which is ring opened with a C 6-18  carboxylic acid; and (c) contacting the emulsion with a demulsifying effective amount of the alkoxylated C 10-24  carboxylic acid ester. Said process has application on crude oil emulsions.

BACKGROUND OF THE INVENTION

This invention relates to a process for breaking emulsions containingwater and oil, preferably aqueous crude oil emulsions.

In the production of crude oils, an increasing amount of water isbrought up with the oil as exploitation of the occurrence progresses.Surface-active substances (for example asphaltenes and resins) presentin the crude oils emulsify most of the water to form highly stablewater-in-oil emulsions. The emulsified water can make up from 0.1 to 90%by weight of the emulsion as a whole. The emulsion water can containdissolved salts which lead to corrosion problems in the processing ofthe crude oil or which—as catalyst poisons—can complicate subsequentprocessing. In addition, the water present in the crude oil leads toincreased transportation costs.

Crude oils differ distinctly in their composition according to theirorigin. In addition, some of the natural emulsifiers present in thecrude oils have a complex chemical composition so that speciallyselected emulsion breakers or demulsifiers have to be used.

The demulsifiers used for aqueous crude oil emulsions are selected froma wide range of different compounds used either individually or in theform of mixtures, for example polyamides, alkylarylsulfonates andphenolic resins (Kim, Y. H., Wasan, D. T., Ind. Eng. Chem. Res. 1996,35, 1141-1149). DE 44 18 800 A1 claims the use of mixtures of knowndemulsifiers with polyalkylene glycol ethers for removing water fromcrude oil. EP 751 203 A2 proposes polymers obtained by reacting certainalkoxylated polyols with aromatic compounds containing reactive groupsas demulsifiers. U.S. Pat. No. 3,928,194 describes a number of differentclasses of compounds as demulsifiers for aqueous crude oil emulsions,including for example glycol esters, fatty acids, fatty add esters,amines, phenolic resins and alkoxylated derivatives thereof.

However, known demulsifiers or mixtures of known demulsifiers are notalways satisfactory because separation of the water and oil phaseseither takes too long or involves an excessive dosage of thedemulsifier. In addition, in view of the widely differing composition ofcrude oils, there is a constant need for improved demulsifiers ordemulsifiers adapted to special crude oil qualities.

Accordingly, the problem addressed by the present invention was toprovide improved demulsifiers for breaking water-in-oil emulsions whichwould be suitable in particular for breaking aqueous crude oilemulsions.

It has been found that emulsions containing water and oil can beeffectively broken if selected alkoxylation products of carboxylic acidesters are added as demulsifiers to the emulsions.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention relates to a process for breakingemulsions containing water and oil into a water phase and an oil phaseby addition of a demulsifier, products of the addition of ethylene oxideand/or propylene oxide onto C₁₀₋₂₄ carboxylic acid esters containing OHgroups being used as demulsifiers.

The process according to the invention is generally suitable forbreaking emulsions containing water and oil. It may be used both foremulsions of the oil-in-water type and for emulsions of the water-in-oiltype. However, the process is preferably used for separating aqueouscrude oil emulsions, i.e. water-in-oil emulsions of which the oil phaseexclusively or predominantly contains crude oil.

DETAILED DESCRIPTION OF THE INVENTION

The esters used as demulsifiers in accordance with the invention areknown and are described, for example, in DE 3923394 A1 of which thedisclosure is also part of the present application.

The demulsifiers used in accordance with the invention may be obtainedby conventional organic syntheses, for example from the epoxides ofunsaturated oils which are ring-opened with suitable reagents and thenreacted with ethylene oxide ardor propylene oxide.

Preferred educts are any OH-free unsaturated C₁₀₋₂₄ carboxylic acids ofnatural and/or synthetic origin with at least one or two double bonds inthe 9 and/or 13 position, for example 9c-dodecenoic acid,9c-tetradecenoic acid, 9c-hexadecenoic acid, 9c-octadecenoic acid,9t-octadecenoic acid, 9c-, 12c-octadecadienoic acid, 9c-, 12c-,15c-octadecatrienoic acid, 9c-eicosenoic acid and/or 13c-docosedenoicacid and/or mixtures with at least a high content of such unsaturatedcarboxylic acids. Preferred educts are carboxylic acids containing 16 to24 carbon atoms and at least one or two double bonds in the 9 and/or 13position or carboxylic acid mixtures with at least a high content ofcarboxylic acids containing 16 to 24 carbon atoms and at least one ortwo double bonds in the 9 ardor 13 position. These may be esterifiedwith alcohols, for example, by conventional synthesis methods. Accordingto the present invention, C₁₀₋₂₄ carboxylic acid esters containing C₂₋₆polyols as their alcohol component are preferably used. The polyolscontain between 2 and 6 OH groups in the molecule. Examples of suchpolyols are diethylene glycol, pentaerythritol, trimethylol propane andglycerol.

However, naturally occurring OH-free unsaturated C₁₀₋₂₄ carboxylic acidesters are preferably used for the production of the demulsifiers usedin accordance with the invention. Demulsifiers based on C₁₀₋₂₄ glycerolesters are preferably used in the process according to the invention.Preferred unsaturated glycerol-based C₁₀₋₂₄ carboxylic acid esters areany mono-, di- or triglycerides which contain at least one or two doublebonds in the 9 and/or 13 position of the C₁₀₋₂₄ carboxylic acid ester,more particularly naturally occurring fats and oils of which thecarboxylic acid content is made up predominantly of unsaturated C₁₀₋₂₄carboxylic acids containing at least one or two double bonds in the 9and/or 13 position. Examples of such naturally occurring unsaturatedglycerides are olive oil, linseed oil, sunflower oil, soybean oil,safflower oil, peanut oil, cottonseed oil, rapeseed oil, palm oil, lard,tallow and fish oil. Demulsifiers based on soybean oil are particularlypreferred.

The unsaturated OH-free C₁₀₋₂₄ carboxylic acid esters are epoxidized byknown methods, for example with per acids or hydrogen peroxide. Theiodine values of the epoxidation products obtained are below 20 andpreferably below 15. The oxirane rings of the epoxidized C₁₀₋₂₄carboxylic acid esters are then opened by reaction with hydrogen orprotic compounds, such as water, linear or branched C₁₋₂₂ alkyl and/oralkenyl alcohols or linear or branched and/or unsaturated C₁₋₂₄carboxylic acids, to form hydroxyl groups. Saturated unbranched C₆₋₁₈fatty acids are preferably used for ring opening.

The OH-containing C₁₀₋₂₄ carboxylic acid esters obtainable by thisopening of the oxirane rings contain at least one free OH group in thecarboxylic acid moiety. Preferred compounds are those which, in the 9/10or 13/14 position at least, contain a structural unit corresponding togeneral formula (I):

in which R¹ is a hydrogen atom or an OH group. Where alcohols were usedto open the oxirane rings, R¹ is an OR² group in which R² is an alkylgroup containing 1 to 22 carbon atoms or an alkenyl group containing 2to 22 carbon atoms. Where C₁₋₂₄ carboxylic acids were used to open theoxirane rings, R² is a group COR³ in which R³ is a hydrogen atom, analkyl group containing 1 to 23 carbon atoms or an alkylene groupcontaining 2 to 23 carbon atoms.

The OH-containing C₁₀₋₂₄ carboxylic acid esters obtained by opening ofthe oxirane rings are then reacted with ethylene oxide and/or propyleneoxide by known methods. The alkoxylated esters used as demulsfilers inthe process according to the invention are preferably obtained byaddition of 1.0 to 2.5 parts of ethylene oxide and/or propylene oxideonto 1 part of the non-alkoxylated ester. Products of the addition of1.5 to 1.8 parts of ethylene oxide and/or propylene oxide onto 1 part ofester are particularly preferred. Esters reacted with ethylene oxideonly are preferably used in the process according to the invention.

Esters obtained by addition of ethylene oxide and/or propylene oxideonto epoxidized C₁₀₋₂₄ carboxylic acid triglycerides, especially soybeanoil epoxides, ring-opened with C₆₋₁₈ carboxylic acids are particularlysuitable for use as demulsifiers in the process according to theinvention.

According to the invention, the emulsions are separated by adding asufficient quantity of demulsifier—normally between 5 and 1,000 ppmactive substance, based on the total quantity of emulsion—to theemulsion. The emulsions then separate automatically into an aqueousphase and an oil phase, generally after a short time, i.e. between 10and 60 minutes. The temperature of the emulsion can be between 0 and100° C. In the separation of crude oil emulsions, the demulsifier may beadded to the crude oil on site. In that case, demulsification generallyproceeds quickly enough, even at the oil production temperature, for theemulsion to separate en route to the preparation stage. Here, it isseparated into pure oil and salt water in an optionally heatedseparator. The demulsification process can be accelerated by stirringthe emulsion after addition of the demulsifiers.

To improve their dosability, the demulsifiers may also be used in theform of a solution in suitable solvents. Suitable solvents, are,generally, organic compounds with boiling temperatures of 50 to 200° C.,for example methanol. Aromatic compounds, such as toluene or xylene orthe mixtures of alkylnaphthalenes marketed by Esso under the name ofSolvesso®, are particularly suitable. Where the demulsifiers are used indissolved form, solutions containing between 0.5 and 50% by weight andpreferably between 10 and 40% by weight of the demulsifier areadvantageously used for demulsification.

EXAMPLES Example 1: Production of the Demulsifier Example 1a

1770 g (7.5 moles, based on epoxide oxygen) of soybean oil epoxide(epoxide oxygen=6.78%) are added with stirring over a period of 1 hourat 150° C. to 1225 g (7.9 moles) of head-fractionated fatty acid (60%C₈, 35% C₁₀, AV 361.9), followed by reaction for 2 hours at 170° C.(epoxide oxygen <0.15%). To remove the excess fatty acid, the reactionmixture is then distilled in vacuo (469 g distillate) up to abottom-product temperature of 200° C. The intermediate product is ayellow clear polyol (viscosity 5550 mPas (20° C.); OHV 105, SV 236, AV3.1).

423 9 (39 parts) of this intermediate product are heated in an autoclaveto 100° C. with 6.9 g of a 30% methanolic potassium hydroxide solution,after which the methanol is removed by 5× evacuation and purging withnitrogen as inert gas. A total of 660 g (61 parts) of ethylene oxide isthen added in portions at 150° C. so that the pressure does not exceed 5bar. On completion of the reaction, the reaction mixture is cooled to80-100° C., evacuated for ca. 15 mins. to remove traces of ethyleneoxide and the catalyst is neutralized with lactic acid. A clear yellowliquid with an OHV of 54.7 is obtained in this way.

Example 1b

Another alkoxylated polyol was prepared as described in Example 1a byreacting 350 g (70 parts) of the intermediate product with 150 g (30parts) of ethylene oxide. OH value 86.

Example 2: Determination of the Demulsifying Effect

90 g of crude oil (Arabian light) were mixed with 10 g tap water and,after the addition of 49.9 ppm (active substance) of demulslfier, theresulting mixture was shaken and its demulsifying effect wassubsequently measured.

To measure the demulsifying effect, sedimentation profiles were measuredover 40 minutes at room temperature. The amount of free water (in % byweight, based on the total quantity of emulsion) was measured after 10and 40 minutes at room temperature as was the transparency of the waterphase.

The demulsifiers were predissolved in Solvesso® 150 (alkylnaphthalenemixture marketed by Esso) and diluted with toluene to form a 10% byvolume solution which was then added to the emulsion. The results areset out in Table 1:

Demulsifiers used

A Dehydem 2F-polyalkylphenol/formaldehyde ethoxylate (Henkel)

Dehypon LT7 -C₁₂₋₁₄ fatty alcohol+7EO (Henkel)

C alkoxylated ester according to Example 1b

D alkoxylated ester according to Example 1a

TABLE 1 Free water after 10 and Transparency of the water phase 40mins.* after 10 and 40 mins.** Demulsifier [% by weight] [%] A 0/8 —/30B —/— —/— C 0/7 —/37 D  2/10  2/45 *max. 10% by weight **100%transparency corresponds to pure water

It can be seen that only the use of compound D according to theinvention leads to both quick and complete separation of the crude oilemulsions.

What is claimed is:
 1. A process for breaking an emulsion into a waterphase and an oil phase comprising: (a) providing an emulsion containingan oil phase and a water phase; (b) providing an alkoxylated C₁₀₋₂₄carboxylic acid ester derived from the addition of ethylene oxide and/orpropylene oxide onto a ring opened epoxidized C₁₀₋₂₄ carboxylic acidtriglyceride which is ring opened with a C₆₋₁₈ carboxylic acid; and (c)contacting the emulsion with a demulsifying effective amount of thealkoxylated C₁₀₋₂₄ carboxylic acid ester.
 2. The process of claim 1wherein the alkoxylated C₁₀₋₂₄ carboxylic acid ester contains from 1.0to 2.5 parts by weight of ethylene oxide and/or propylene oxide, per 1part by weight of non-alkoxylated C₁₀₋₂₄ carboxylic acid ester.
 3. Theprocess of claim 1 wherein the alkoxylated C₁₀₋₂₄ carboxylic acid estercontains from 1.5 to 1.8 parts by weight of ethylene oxide and/orpropylene oxide, per 1 part by weight of non-alkoxylated C₁₀₋₂₄carboxylic acid ester.
 4. The process of claim 1 wherein the C₁₀₋₂₄carboxylic acid ester from which the alkoxylated C₁₀₋₂₄ carboxylic acidester is derived contains, in the 9/10 or 13/14 position, a structuralunit corresponding to formula (I):

wherein R¹ is OR² group wherein R² is COR³ group wherein R³ is an alkylgroup containing 5 to 17 carbon atoms.
 5. The process of claim 1 whereinthe oil phase comprises crude oil.
 6. The process of claim 1 wherein theemulsion is contacted with from 5 to 1,000 ppm active substance, of thealkoxylated C₁₀₋₂₄ carboxylic acid ester.
 7. The process of claim 1wherein the alkoxylated C₁₀₋₂₄ carboxylic acid ester is present in anorganic solvent having a boiling point of from 50 to 200° C.
 8. Theprocess of claim 7 wherein the alkoxylated C₁₀₋₂₄ carboxylic acid esteris present in the solvent in an amount of from 0.5 to 50% by weight. 9.The process of claim 7 wherein the emulsion has a temperature of from 0to 100° C.